Checking syslog availability before starting vdsm

If logger is not able to open /dev/log, it throws exception and vdsm
does not start. This path verifies that this file exist and fail vdsm
start if not.

Change-Id: I60d0537f67da3cf81477760ccb3760a103dc15ac
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=928861
Signed-off-by: Yaniv Bronhaim <ybronhei@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/13547
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Reviewed-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Tested-by: Douglas Schilling Landgraf <dougsland@redhat.com>